Trying to trace source of non-working op-amps

Anton Erasmus wrote in news: snipped-for-privacy@4ax.com:

A quick google search on "electronics manufacturers logo" yields the following as the 4th link.

Only "F" I see there is Fairchild Semiconductors, which was my first guess anyway.

HTH

--
Richard

When the opamp is "not working at all" what voltage do you see at the plus input, the minus input and the output? If you put the opamp in a test circuit, does it work (in other words are they only bad when installed on your board or always bad)?

--
Guy Macon, Electronics Engineer & Project Manager.  Remember Doc Brown 
from the 'Back to the Future' movies?  Do you have an "impossible" 
engineering project that only someone like Doc Brown can solve? 
Check out my resume at http://www.guymacon.com/resume.html/

Fairchild or Fujitsu.

Hi Anton,

Is this device in a very tiny surface-mount package, with abbreviated package markings? Are you sure that the chips you bought before are actually TL074s?

Listed vendors for the TL074 are:

ST Microelectronics Motorola Semiconductor Products ON Semiconductor Texas Instruments

also:

National Semiconductor (M38510/11906BCA, military version)

None of those has a logo that looks like an "F"...

Hi,

Thanks for the response. I could also only find Fairchild with an F logo. I was hoping for some site with maybe more obscure manufacturers logos. The component suppliers here in South Africa sometimes buy from extremely odd places for "standard" components. (74 series, Op-Amps,

4000 series etc.) Sometimes these companies have logos that on first glance are quite similar to the main stream semiconductor logos. Unfortunately even though we specificially specify the more main stream seimconductor part numbers, it sometimes happen that the buyers get told by the suppliers that the component is an exact equivalent at a 10th of the price, and they cannot resist. Most of the time this is not a problem, but if these devices are really from Fairchild Semiconductors (a company from I do not expect or suspect of supplying dofgy devices), then I need to find out the problem.

Regards Anton Erasmus

Hi,

The circuit is a stock standard non-inverting amplifier with a gain of about 20. This particular board has been manufactured in batches of

100 every 3 months or so for the last 10 years. We have had problems with dodgy TL074s once before, but then the components came from some obscure semiconductor house in India. With the non-inverting Amp isolated from the rest of the circuit, then one basically get nothing out no matter what the input is. The chips seems completely "dead". Replacing the chip with a TL074 from TI, or with any other quad op-amp we had lying around, then the circuit works as expected. We have had ICs from obscure semiconductor houses in the past, who's logos at first glance looks very much like the "Big" semiconductor houses. The dodgy TL074s logos looks like Fairchild Semicondcutor's. I have never experienced or even heard of Fairchild's devices working other than as specified. If I can establish from where these devices came, then I can at least try and ensure that we do not buy from that supplier again.

Regards Anton Erasmus

Component subsitution is becoming a problem, particularly with common garden variety parts, and suppliers who aren't authorised dealers. They may be manufacturered by dodgy component makers who may have a very basic semiconductor manufacturing facility set up, or the components may be castoffs from the major semi manufacturers that didn't come up to spec at various testing stages and were stolen/sold off to experimenters/whoever. They may even be legitimate cheaper components that have had their correct markings removed, and markings of a more expensive component substituted.

Some examples of fake components have been power transistors that were used in audio amplifier kits here in Australia. These had markings that at first glance indicated that they were made in Mexico, but when you looked closer, it actually said "MEX1CO", ie. substituting a "1" where an "I" should have been. When the amplifier was first turned on/cranked up, the output transistors destroyed themselves. The owner usually went back to the shop where they bought the kit, and purchased replacement transistors. More often than not, accidently purchasing more fakes, until the the method of identification was found.

Fake pentium cpus have been getting around for years.

The only way to be assured of purchasing genuine components is to deal ONLY with the manufacturer, or it's legitimate representatives.

--

Regards
David

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